I'm tihnking about a possible MUD, that actually encourages botting. Game-play wise, this would be a playground for programmers. I o the idea, after someone told me about a uiversity course about social interactions between programs, or the like.

The audience would include (at least) everyone who likes programming games, MUD-programmers who want a testbed for their smarter mobs, curious mudders who want to see a world populized by said smart mobs, hopefully normal mudders, folks interested in playing with swarm intelligence.

Important features would be player-skill based ways of problem solving (including combat), so pogramming isn't too trivial. (possibly with afeguards against bots becoming too powerful, e.g. combat is player-controlled, but only one command every second is parsed)
The power one can gain from grinding should be low compared to power gains from other styles of play, e.g. system of randomly creating quests - so there is actually a reason for human players to stick around
a possibility to play roles normaly reserved to mobs, epecially wildlive - so there is, for example, an incentive to program a smart wolf, or smart sheep.

A system that awards programming certain feats (possibly awarding only published code): Fooling human players into thinking that a bot is indeed a human player (maybe made easieer because of the less-than-average communication skills some people display online), coding decent communication using only in-game means (say, emote) - possibly with quite limited emotes (think a pack of wolves).

A down-tuned version would be a way to programm pets extensivly, though this would deny players to code in their favorite language, and would be possibly harder to implement.

In summary, a MUD like this (depending how much code is published) would capitalize on one strength of MUDs - player generated content in a new way and could lead to code or experience that improves other games. Whille possibly not apealling to the average mudder (whoever he is), there are probably enough nerds about to keep such a thing alive.

Of course, maybe I'm decade behind, and such a thing exists already. Any comments?

You might want to read up on RobotWar, and the games it inspired (some of which are still around and are open source). They are basically pure PK games, but the same sort of concept could certainly be extended to other activities.

It could prove difficult to appeal to human players if most of the other players are bots, though.

I quite like the idea of writing short scripts that other players could then combine in other ways; if all players were assumed to have a great number of minions it might compel more players to stick around and play at the same time.

This fits with a game idea I had where players play wizard-king kinds of PCs, each starting the game with a small tower in the game world; as PCs recruit minions they gain the ability to switch their point-of-view into that minion (into your pack of wolves for example). Perhaps your minion abilities would be limited to either the scripts you write, or scripts you buy for gold in a kind of 'spell market'.